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scouring cannot occur. When wire or polymeric back-up support <br /> mesh is used, the wire or polymeric mesh shall extend into the <br /> ground 3-inches min. <br /> 9. Drive or place the fence posts into the ground 18-inches min. A <br /> 12—inch min. depth is allowed if topsoil or other soft subgrade soil <br /> is not present and 18-inches cannot be reached. Increase fence post <br /> min. depths by 6 inches if the fence is located on slopes of 3H:1 V <br /> or steeper and the slope is perpendicular to the fence. if required <br /> post depths cannot be obtained, the posts shall be adequately <br /> secured by bracing or guying to prevent overturning of the fence <br /> due to sediment loading. <br /> 10. Use wood, steel or equivalent posts. The spacing of the support <br /> posts shall be a maximum of 6-feet. Hosts shall consist of either: <br /> • Wood with dimensions of 2-inches by 2-inches wide min. and <br /> a Meet min. length. Wood posts shall be free of defects such <br /> as knots, splits,or gouges. <br /> • No. 6 steel rebar or larger. <br /> • ASTM A 120 steel pipe with a minimum diameter of 1-inch. <br /> • U, T,L, or C shape steel posts with a minimum weight of 1.35 <br /> lbs./ft. <br /> • Other steel posts having equivalent strength and bending <br /> resistance to the post sizes listed above. <br /> 11. Locate silt fences on contour as much as possible,except at the <br /> ends of the fence, where the fence shall be turned uphill such that <br /> the silt fence captures the runoff water and prevents water from <br /> flowing around the end of the fence. <br /> 12. if the fence must cross contours, with the exception of the ends of <br /> the fence, place gravel check dams perpendicular to the back of the <br /> fence to minimize concentrated flow and erosion. The slope of the <br /> fence line where contours must be crossed shall not be steeper than <br /> 3HAV. <br /> • Gravel check dams shall be approximately 1-foot deep at the <br /> back of the fence. Gravel check dams shall be continued <br /> perpendicular to the fence at the same elevation until the top of <br /> the check dam intercepts the ground surface behind the fence. <br /> • Gravel check dams shall consist of crushed surfacing base <br /> course, gravel backfill for walls, or shoulder ballast. Gravel <br /> check dams shall be located every 10 feet along the fence <br /> where the fence must cross contours. <br /> • Refer to .Figure 4.2.13 for slicing method details. Silt fence installation <br /> using the slicing method specifications: <br /> l"ohone 11—Consh-uction Stornzwaler Pollution Pr•erention-August 2012 <br /> 4-91 <br />